Toxin gene from Xenorhabdus nematophilus

ABSTRACT

Purified insecticidal toxins and biologically active fragments thereof, and polynucleotide molecules encoding same, from the bacteria Xenorhabdus nematophilus are described.

This application is a filing under 35 U.S.C. 371 of PCT/AU94/00348 filed Jun. 24, 1994.

TECHNICAL FIELD

The present invention concerns the identification and isolation of a new class of protein toxins specific against insects which are produced by bacteria from the species Xenorhabdus nematophilus and possibly by the species X.beddingii. In addition, the present invention relates to the insertion of this class of toxin into recombinant viruses, bacteria, protozoa, fungi, and transgenic plants in order to broaden the use of these toxins for control of a large range of insect pests and plant parasitic nematodes.

BACKGROUND

Insect pathogenic nematodes of the family Steinernematidae are known to be symbiotically associated with bacteria of the genus Xenorhabdus. It has been observed that these bacteria have the ability to kill a wide range of different insects without the aid of their nematode partners.

The present inventors have identified a new class of toxins. A DNA fragment encoding one of these toxins has been isolated from Xenorhabdus nematophilus stain A24 and characterised by sequencing. As will be recogised by persons skilled in the art, DNA fragments encoding members of this new class of toxins may be usefully introduced into viral agents, including entomopox and nuclear polyhedrosis viruses; bacteria (including Gracilicutes, Firmicutes, Tenericutes and Mendosicutes); fungi; protozoa; and plants.

SUMMARY OF THE PRESENT INVENTION

In a first aspect, the present invention consists in a polynucleotide molecule comprising a nucleotide sequence which encodes an insecticidal toxin and which is at least 70% homologous to the nucleotide sequence shown in Table 1 from residue 83 to 919 (SEQ ID NO:1), or a fragment thereof which fragment encodes an insecticidal polypeptide.

In a preferred embodiment of the present invention the nucleotide sequence is at least 90% homologous to the sequence shown in Table 1 from residue 83 to 919 (SEQ ID NO:1).

Preferably, the nucleotide sequence which encodes an insecticidal toxin from Xenorhabdus and more preferably, the nucleotide sequence substantially corresponds to the sequence shown in Table 1 from residue 83 to 919 (SEQ ID NO:1).

In a second aspect the present invention provides an insecticidal toxin which includes an amino acid sequence which is at least 70% homologous to residues 1 to 278 (SEQ ID NO:2) shown in Table 2 or a functional fragment thereof.

In a preferred embodiment of the present invention the insecticidal toxin includes an amino acid sequence which is at least 90% homologous to residues 1 to 278 (SEQ ID NO:2) shown in Table 2 or a functional fragment thereof.

In a further preferred embodiment the insecticidal toxin includes an amino acid sequence substantially corresponding to residues 1 to 278 (SEQ ID NO:2) in Table 2 or a functional fragment thereof.

In a third aspect the present invention provides a recombinant organism, the organism being characterised in that it is transformed with the polynucleotide molecule of the first aspect of the present invention.

The organisms which may be usefully transformed with the polynucleotide molecule of the first aspect of the present invention include viral agents such as entomopox and nuclear polyhedrosis viruses; bacteria, such as Gracilicutes, Firmicutes, Tenericutes and Mendosicutes; fungi; protozoa; and plants.

The term "substantially corresponds" as used herein in relation to the nucleotide sequence is intended to encompass minor variations in the nucleotide sequence which due to degeneracy do not result in a change in the encoded protein. Further this term is intended to encompass other minor variations in the sequence which may be required to enhance expression in a particular system but in which the variations do not result in a decrease in biological activity of the encoded protein.

The term "substantially corresponding" is used herein in relation to the amino acid sequence is intended to encompass minor variations in the amino acid sequence which do not result in a decrease in biological activity of the insecticidal toxin. These variations may include conservative amino acid substitutions. The substitutions envisaged are:

G, A, V, I, L, M; D, E; N, Q; S, T; K, R, H; F, Y, W, H; and P, Nα-alkylamino acids.

As used herein the term "functional fragments" is intended to encompass fragments of the insecticidal toxin which retain insecticidal activity.

In a fourth aspect, the present invention provides a method for controlling the proliferation of insects, comprising applying to an infested area a recombinant organism according to the third aspect optionally in admixture with an acceptable agricultural carrier.

Isolation and Characterisation of a Toxin from Xenorhabdus nematophilus A24

Generation of a Cosmid Library

Genomic DNA from Xenorhabdus nematophilus A24, isolated using the method of Marmur (1961) was partially digested using the restriction enzyme Sau 3A, to generate fragments of DNA that were in the size range of 30 to 50 kilobasepairs (kb), and dephosphorylated using the enzyme calf alkaline phosphatase. The cosmid "Supercos" (Stratagene) was prepared to receive foreign insert DNA into its Bam HI cloning site according to the manufacturer's instructions. The digested DNA from X.nematophilus A24 was added to the cosmid DNA in a ratio of 3:1 and ligated together using the enzyme T4 DNA ligase. The ligated material was subsequently packaged into λ-bacteriophage using the Gigapack II XL Packaging Extract (Stratagene) as per the manufacturer's instructions. The packaged DNA was subsequently transfected into the Escherichia coli strain NM554 (F-, recA, araD139,Δ (ara, leu) 7696, Δlac Y74, galU-, galK-, hsr, hsm⁺, strA, mcrA[-], mcrB[-]. Bacteria were plated out onto Luria Bertani (LB) agar plates containing 150 μg ml⁻¹ ampicillin to select for those bacteria containing recombinant Supercos plasmids.

Screening for Toxin Producing Clones

Individual clones were grown overnight at 28° C. in LB containing 150 μg ml⁻¹ ampicillin. Cultures were treated for 15 minutes with 2 mg ml⁻¹ lysozyme in order to release any proteins produced by the recombinant DNA into the medium. Five μl aliquots of this solution were then injected directly into the haemocoel of three Galleria mellonella fourth instar larvae. Appropriate controls containing lysozyme and non-recombinant E.coli NM554 cultures were also injected to confirm the absence of any toxicity to these larvae. Two clones were found to have strong insecticidal activity. Injected larvae were found to be very sluggish after 30 hours, with all larvae dead within three days.

Characterisation of Toxin Producing Clones

The recombinant Supercos DNA from these clones was isolated using an alkaline lysis procedure (Maniatis et al., 1982). Isolated DNA was digested with varying restriction enzymes and analysed using TAE agarose gel electrophoresis (Maniatis et al, 1982). It was found that both clones were identical and contained a 34.6 kb DNA insert from X. nematophilus A24. One of these clones cos149 was chosen for further study.

A 7.4 kb Bam HI fragment from cos149 was cloned into the plasmid vector pGEM7Z(f)+ (Promega) which was transformed into the E.coli strain DH5α (F-, Φ80dlac ZΔ M15, recA1, endA1, gyrA96, thi-1, hsdR17[r_(K-), m_(K+) ]sup E44, relA1, deoR, Δ[lacZYA-argF] U169) using electroporation at 25 μF, 200 Ω and 2.5 kV in a 0.2 cm cuvette in a Bio-Rad Gene Pulser. This clone (N8pGEM) was found to continue to be toxic against G.mellonella larvae.

Plasmid DNA from N8pGEM was isolated and digested with the restriction enzymes ClaI and SphI. This resulted in the linearization of this plasmid containing one end (3') which was resistant to digestion by the enzyme Exonuclease III and the other end (5') which could be digested at a constant rate of 450 bases per minute at 37° C. by this enzyme using the Erase-a-Base kit from Promega. Using this enzyme aliquots containing decreasing size plasmids were obtained which were recircularised using the enzyme T4 DNA ligase. Recircularised plasmids were reintroduced into the bacterium E.coli strain DH5α using electroporation (see above). Varying size clones were selected and used for injecting G.mellonella larvae. The smallest clone which continued to be insecticidal was found to contain 1.5 kb of X.nematophilus A24 DNA and was designated tox 1.

Plasmid DNA from tox 1 was isolated and digested with the restriction enzymes Sac I and HindIII, respectively to again create linear molecules with one end resistant and the other sensitive to digestion with Exonuclease III. Deletion mutants were isolated and tested against G.mellonella larvae. A clone which now only contained 1.2 kb of X.nematophilus A24 DNA was isolated and was toxic against our test insect. This clone was designated toxb4.

The recombinant plasmids from toxb4 and three further (non-toxic) deletion clones, toxb5, toxb6 and toxb7, were isolated and used for obtaining the sequence of both strands of the toxin gene. Sequencing was performed using the Applied Biosystems, Incorporated Model 370 automated sequencer. Sequencing templates were prepared using double stranded DNA templates and the 21M13 and SP6 primer sites located on the pGEM7Z(f)+ plasmid and using the Taq dye primer cycle sequencing protocol (Applied Biosystems, Incorporated).

The toxin gene was found to consist of an 834 basepair open reading frame (Table 1) (SEQ ID NO:3) which translates into a 278 amino acid protein (Table 2) (SEQ ID NO:2). The start of the toxin gene sequence was preceded by appropriate DNA promoters necessary for transcription of the gene into a mRNA molecule prior to its synthesis into a peptide. These consist of a Shine-Dalgarno poly-purine sequence and -10 and -35 RNA polymerase recognition sequences (Table 1).

The DNA sequence and the derived amino acid sequences were analysed by sequence data bank analyses to determine if any other related sequences have previously been identified. The results indicated that no other sequence exists in the GenBank and EMBL data banks which has any similarity to this gene and its product.

Cloning of Xenorhabdus Toxin into a High-Expression Vector

Using the determined DNA sequence, 20-mer DNA primers were designed to cover the 5' and 3' region of the toxin gene and thus allow PCR amplification of the toxin and subsequent insertion into an expression vector. These primers included linker regions containing appropriate restriction enzyme sites (ClaI and NdeI for the 5' primer and Bam HI for the 3' primer).

5' primer CCATCGATCATATGGTTATTAAACC (SEQ ID NO:4)

3' primer CGGGATCCTTATCTCTAAGGTTTTT (SEQ ID NO:5)

Utilising a standard PCR protocol (Innis, M. A., Gelford, D. H., Sminsky, J. J. and White, T. J.: (1990). PCR Protocols : A Guide to Methods and Applications. Academic Press, San Diego. 482pp) the toxin was amplified out of the genome of X.nematophilus A24 and restriction digested with Cla I and Bam HI. The digested fragment was subsequently ligated into pGEM-7Zf(+) and then subcloned from this vector into the high expression vector pT7T2b(derived from pET11 [Novagen] and carrying the T7 promoter upstream from the start of the toxin insert; constructed by Dr. Karl Gordon, CSIRO, Division of Entomology) using the restriction enzyme sites Nde I and Bam HI. The recombinant plasmid was transformed into the E. coli strain BL21(DE3)[F-ompT r_(B) -m_(B) -, which carries in its chromosome the T7 RNA polymerase gene under lac UV5 control). Induction of the toxin may be achieved by the addition of 0.4 mM IPTG at mid-exponential phase of the culture and continuing the incubation for an extra 4 hours.

In vitro expression of the 1.2 Kb insert fragment from toxb4 was achieved with the E.c. S30 Extract Procaryotic Translation System for linear DNA. Only a 30 kDa peptide was produced indicating that the 1.2 Kb fragment encodes one peptide only--the insect toxin.

Southern Blot Hybridization of a Range of Xenorhabdus species and Photohabdus Luminescens Strains with the X.nematophilus A24 Toxin Gene

DNA isolated from a range of Xenorhabdus species and Photohabdus (bacteria symbiotically associated with nematodes from the family Heterohabditidae) controls was digested to completion with the restriction enzyme Eco RV and run out on a 0.8% TAE agarose gel and the DNA fragments blotted and fixed onto a Hybond-N+ membrane (Amersham) as per the manufacturer's instructions.

The toxin gene was radiolabelled with ³² p using nick translation (Maniatis et al., 1982) and probed against the blot containing the DNA of a range of Xenorhabdus and Photohabdus strains (Maniatis et al., 1982). Under moderate stringency wash conditions at 65° C.(0.1% SDS, 1% SSPE, Maniatis et al, 1982) the toxin only hybridised to X. nematophilus and X. beddingii strains. However, the toxin gene did not show any homology to the DNA from strains of X. bovienli, X. poinarii, some unclassified Xenorhabdus spp. and Photohabdus luminescens. This result suggests that this toxin type is confined to strains from the species X. nematophilus and X. beddingii. As X. beddingii has insecticidal activity and shows homology to the toxin gene it is most probable that these sequences are part of related/similar yet slightly different toxins. A high stringency wash at 65° C.(0.1% SDS, 0.1% SSPE; Maniatis et al. 1982) of the blot removed the message from the X.beddingii strain, but not from the X.nematophilus strains.

Characteristics of the Toxic Protein Product

The toxin is inactivated by heating to 65° C. for 15 minutes, yet stable at 45° C. Sodium dodecyl sulphate at a concentration of 0.1% does not inactivate this toxin thereby indicating extreme stability and thereby a protein which will fold into its appropriate form under a wide range of different conditions (which includes most cell types).

This new class of toxin may be purified by one or more methods of protein purification well known in the art. Insecticidal fragments may be generated from the purified toxin using, for example, cleavage with trypsin or cyanogen bromide.

As will be appreciated by those skilled in this field, the present invention provides a new class of toxins useful for genetically engineering a wide range of biological systems which will thus become more useful for control of insect pests detrimental to agricultural, aquatic and forest industries.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

                                      TABLE 1                                      __________________________________________________________________________     1  AAGAAACCGT AACAGCGGAA ATCAACGCTG CAATTTATAT TAGTAGTCAT                                                           SEQ ID NO:6                                                                  Start           -35                         51 TTCAATAAAC GCCAACATAA TGGGAAAGTA CAATGGTTAT TAAACCCGTA                                          -10     S-D                                                101                                                                               ACAACTCCGA GTGTAATACA ATTAACGCCT GATGATAGAG TAACGCCTGA                      151                                                                               TGATAAAGGT GAATATCAAC CCGTTGAAAA GCAAATAGCG GGAGATATAA                      201                                                                               TACGTGTACT AGAATTCAAG CAAACAAATG AAAGTCATAC AGGATTGTAT                      251                                                                               GGAATTCCAT ATCGAGCTAA GAAAGTAATA ATAGCATATG CTTTAGCGGT                      301                                                                               AAGTGGTATT CATAATGTCT CTCAACTTCC AGAAGACTAT TATAAAAATA                      351                                                                               AGGATAACAC AGGTAGAATT TATCAAGTAT ACATGTCTAA TCTTTTATCT                      401                                                                               GCACTATTGG GTGAGAATGG TGATCAAATT TCTAAAGATA TGGCAAATGA                      451                                                                               TTTTACCCAG AACGAACTGG AGTTTGAGGT CAACGTCTTA AAAATACCTG                      501                                                                               GGATATTCCT GATCTTGAGA ATAAACTATT GGAAGATTTA TTCAGATGAA                      551                                                                               GATAAATTAT TAGCACTATA TTTCTTTGCT TCACAAGAAC TTCCAATGGA                      601                                                                               GGCAAATCAA CAATCAAATG CAGCAAATTT TTTTAAAGTA ATTGATTTTT                      651                                                                               TACTTATCTT ATCTGCTGTA ACATCACTGG GAAAAAGGAT TTTTTCAAAA                      701                                                                               AATTTTTACA ATGGTCTAGA AACTAAATCA TTAGAGAATT ATATTGAGAG                      751                                                                               AAAAAAACTT TCTAAACCTT TCTTTCGACC ACCGCAGAAG TTACCTGATG                      801                                                                               GCAGAACAGG CTACTTGGCC GGTCCAACAA AAGCGCCTAA ATTGCCAACA                      851                                                                               ACGTCTTCTA CAGCAACAAC GTCTACAGCA GCTTCATCTA ATTGGAGAGT                      901                                                                               TAGTTTGCAA AAACCTTAGA GATAACCCAT CCAGAAATAC ATTTATGAAA                                         Stop                                                        951                                                                               ATGGATGATG CTGCAAAACG AAAATATAGT TCATTTATAA AAGAGGTACA                      1001                                                                              AAAGGGTAAT GATCCACGTG CAGCAGCAGC AAGTATTGGT ACAAAAAGCG                      1051                                                                              GCAGTAACTT CGAAAAACTG CAAGGTAGAG ATTTATATAG TATAAGACTA                      1101                                                                              AGCCAAGAAC ACAGGGTAAC ATTCTCCATA AATAATACTG ACCAAATAAT                      1151                                                                              GGAGATCCAA AGTGTTGGAA CTCATTACCA AAATATATAA CCTGATTTAT                      1201                                                                              AGTAGTGATA AGACGTAAGA TAAATATGGA AGGTTGTAAT TCTATTGCAC                      1251                                                                              TTCCTCAGAG GTGACCGCTC AG                                                    __________________________________________________________________________

                                      TABLE 2                                      __________________________________________________________________________     1  MVIKPVTTPS VIQLTPDDRV TPDDKGEYQP VEKQIAGDII RVLEFKQTNE                                                           SEQ ID NO:7                               51 SHTGLYGIPY RAKKVIIAYA LAVSGIHNVS QLPEDYYKNK DNTGRIYQVY                      101                                                                               MSNLLSALLG ENGDQISKDM ANDFTQNELE FEVNVLKIPG IFLILRINYW                      151                                                                               KIYSDEDKLL ALYFFASQEL PMEANQQSNA ANFFKVIDFL LILSAVTSLG                      201                                                                               KRIFSKNFYN GLETKSLENY IERKKLSKPF FRPPQKLPDG RTGYLAGPTK                      251                                                                               APKLPTTSST ATTSTAASSN WRVSLOKP*R *PIQKYIYEN G*CCKTKI*F                      301                                                                               IYKRGTKG** STCSSSKYWY KKRQ*LRKTA R*RFI*YKTK PRTQGNILHK                      351                                                                               *Y*PNNGDPK CWNSLPKYIT *FIVVIRRKI NMEGCNSIAL PQR*PL                          __________________________________________________________________________

    __________________________________________________________________________     #             SEQUENCE LISTING                                                 - (1) GENERAL INFORMATION:                                                     -    (iii) NUMBER OF SEQUENCES: 7                                              - (2) INFORMATION FOR SEQ ID NO:1:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 837 base                                                           (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: DNA (genomic)                                        #ID NO:1: (xi) SEQUENCE DESCRIPTION: SEQ                                       - ATGGTTATTA AACCCGTAAC AACTCCGAGT GTAATACAAT TAACGCCTGA TG - #ATAGAGTA          60                                                                           - ACGCCTGATG ATAAAGGTGA ATATCAACCC GTTGAAAAGC AAATAGCGGG AG - #ATATAATA         120                                                                           - CGTGTACTAG AATTCAAGCA AACAAATGAA AGTCATACAG GATTGTATGG AA - #TTCCATAT         180                                                                           - CGAGCTAAGA AAGTAATAAT AGCATATGCT TTAGCGGTAA GTGGTATTCA TA - #ATGTCTCT         240                                                                           - CAACTTCCAG AAGACTATTA TAAAAATAAG GATAACACAG GTAGAATTTA TC - #AAGTATAC         300                                                                           - ATGTCTAATC TTTTATCTGC ACTATTGGGT GAGAATGGTG ATCAAATTTC TA - #AAGATATG         360                                                                           - GCAAATGATT TTACCCAGAA CGAACTGGAG TTTGAGGTCA ACGTCTTAAA AA - #TACCTGGG         420                                                                           - ATATTCCTGA TCTTGAGAAT AAACTATTGG AAGATTTATT CAGATGAAGA TA - #AATTATTA         480                                                                           - GCACTATATT TCTTTGCTTC ACAAGAACTT CCAATGGAGG CAAATCAACA AT - #CAAATGCA         540                                                                           - GCAAATTTTT TTAAAGTAAT TGATTTTTTA CTTATCTTAT CTGCTGTAAC AT - #CACTGGGA         600                                                                           - AAAAGGATTT TTTCAAAAAA TTTTTACAAT GGTCTAGAAA CTAAATCATT AG - #AGAATTAT         660                                                                           - ATTGAGAGAA AAAAACTTTC TAAACCTTTC TTTCGACCAC CGCAGAAGTT AC - #CTGATGGC         720                                                                           - AGAACAGGCT ACTTGGCCGG TCCAACAAAA GCGCCTAAAT TGCCAACAAC GT - #CTTCTACA         780                                                                           - GCAACAACGT CTACAGCAGC TTCATCTAAT TGGAGAGTTA GTTTGCAAAA AC - #CTTAG            837                                                                           - (2) INFORMATION FOR SEQ ID NO:2:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #acids    (A) LENGTH: 278 amino                                                          (B) TYPE: amino acid                                                           (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: protein                                              #ID NO:2: (xi) SEQUENCE DESCRIPTION: SEQ                                       -      Met Val Ile Lys Pro Val Thr Thr - # Pro Ser Val Ile Gln Leu Thr         Pro                                                                            #   15                                                                         -      Asp Asp Arg Val Thr Pro Asp Asp - # Lys Gly Glu Tyr Gln Pro Val         Glu                                                                            #                 30                                                           -      Lys Gln Ile Ala Gly Asp Ile Ile - # Arg Val Leu Glu Phe Lys Gln         Thr                                                                            #             45                                                               -      Asn Glu Ser His Thr Gly Leu Tyr - # Gly Ile Pro Tyr Arg Ala Lys         Lys                                                                            #         60                                                                   -      Val Ile Ile Ala Tyr Ala Leu Ala - # Val Ser Gly Ile His Asn Val         Ser                                                                            #     80                                                                       -      Gln Leu Pro Glu Asp Tyr Tyr Lys - # Asn Lys Asp Asn Thr Gly Arg         Ile                                                                            #   95                                                                         -      Tyr Gln Val Tyr Met Ser Asn Leu - # Leu Ser Ala Leu Leu Gly Glu         Asn                                                                            #                110                                                           -      Gly Asp Gln Ile Ser Lys Asp Met - # Ala Asn Asp Phe Thr Gln Asn         Glu                                                                            #            125                                                               -      Leu Glu Phe Glu Val Asn Val Leu - # Lys Ile Pro Gly Ile Phe Leu         Ile                                                                            #        140                                                                   -      Leu Arg Ile Asn Tyr Trp Lys Ile - # Tyr Ser Asp Glu Asp Lys Leu         Leu                                                                            #    160                                                                       -      Ala Leu Tyr Phe Phe Ala Ser Gln - # Glu Leu Pro Met Glu Ala Asn         Gln                                                                            #   175                                                                        -      Gln Ser Asn Ala Ala Asn Phe Phe - # Lys Val Ile Asp Phe Leu Leu         Ile                                                                            #                190                                                           -      Leu Ser Ala Val Thr Ser Leu Gly - # Lys Arg Ile Phe Ser Lys Asn         Phe                                                                            #            205                                                               -      Tyr Asn Gly Leu Glu Thr Lys Ser - # Leu Glu Asn Tyr Ile Glu Arg         Lys                                                                            #        220                                                                   -      Lys Leu Ser Lys Pro Phe Phe Arg - # Pro Pro Gln Lys Leu Pro Asp         Gly                                                                            #    240                                                                       -      Arg Thr Gly Tyr Leu Ala Gly Pro - # Thr Lys Ala Pro Lys Leu Pro         Thr                                                                            #   255                                                                        -      Thr Ser Ser Thr Ala Thr Thr Ser - # Thr Ala Ala Ser Ser Asn Trp         Arg                                                                            #                270                                                           -      Val Ser Leu Gln Lys Pro                                                              275                                                               - (2) INFORMATION FOR SEQ ID NO:3:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 834 base                                                           (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: DNA (genomic)                                        #ID NO:3: (xi) SEQUENCE DESCRIPTION: SEQ                                       - ATGGTTATTA AACCCGTAAC AACTCCGAGT GTAATACAAT TAACGCCTGA TG - #ATAGAGTA          60                                                                           - ACGCCTGATG ATAAAGGTGA ATATCAACCC GTTGAAAAGC AAATAGCGGG AG - #ATATAATA         120                                                                           - CGTGTACTAG AATTCAAGCA AACAAATGAA AGTCATACAG GATTGTATGG AA - #TTCCATAT         180                                                                           - CGAGCTAAGA AAGTAATAAT AGCATATGCT TTAGCGGTAA GTGGTATTCA TA - #ATGTCTCT         240                                                                           - CAACTTCCAG AAGACTATTA TAAAAATAAG GATAACACAG GTAGAATTTA TC - #AAGTATAC         300                                                                           - ATGTCTAATC TTTTATCTGC ACTATTGGGT GAGAATGGTG ATCAAATTTC TA - #AAGATATG         360                                                                           - GCAAATGATT TTACCCAGAA CGAACTGGAG TTTGAGGTCA ACGTCTTAAA AA - #TACCTGGG         420                                                                           - ATATTCCTGA TCTTGAGAAT AAACTATTGG AAGATTTATT CAGATGAAGA TA - #AATTATTA         480                                                                           - GCACTATATT TCTTTGCTTC ACAAGAACTT CCAATGGAGG CAAATCAACA AT - #CAAATGCA         540                                                                           - GCAAATTTTT TTAAAGTAAT TGATTTTTTA CTTATCTTAT CTGCTGTAAC AT - #CACTGGGA         600                                                                           - AAAAGGATTT TTTCAAAAAA TTTTTACAAT GGTCTAGAAA CTAAATCATT AG - #AGAATTAT         660                                                                           - ATTGAGAGAA AAAAACTTTC TAAACCTTTC TTTCGACCAC CGCAGAAGTT AC - #CTGATGGC         720                                                                           - AGAACAGGCT ACTTGGCCGG TCCAACAAAA GCGCCTAAAT TGCCAACAAC GT - #CTTCTACA         780                                                                           - GCAACAACGT CTACAGCAGC TTCATCTAAT TGGAGAGTTA GTTTGCAAAA AC - #CT               834                                                                           - (2) INFORMATION FOR SEQ ID NO:4:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 25 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: DNA (genomic)                                        #ID NO:4: (xi) SEQUENCE DESCRIPTION: SEQ                                       #               25 TATT AAACC                                                  - (2) INFORMATION FOR SEQ ID NO:5:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 25 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: DNA (genomic)                                        #ID NO:5: (xi) SEQUENCE DESCRIPTION: SEQ                                       #               25 AAGG TTTTT                                                  - (2) INFORMATION FOR SEQ ID NO:6:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 1272 base                                                          (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: DNA (genomic)                                        #ID NO:6: (xi) SEQUENCE DESCRIPTION: SEQ                                       - AAGAAACCGT AACAGCGGAA ATCAACGCTG CAATTTATAT TAGTAGTCAT TT - #CAATAAAC          60                                                                           - GCCAACATAA TGGGAAAGTA CAATGGTTAT TAAACCCGTA ACAACTCCGA GT - #GTAATACA         120                                                                           - ATTAACGCCT GATGATAGAG TAACGCCTGA TGATAAAGGT GAATATCAAC CC - #GTTGAAAA         180                                                                           - GCAAATAGCG GGAGATATAA TACGTGTACT AGAATTCAAG CAAACAAATG AA - #AGTCATAC         240                                                                           - AGGATTGTAT GGAATTCCAT ATCGAGCTAA GAAAGTAATA ATAGCATATG CT - #TTAGCGGT         300                                                                           - AAGTGGTATT CATAATGTCT CTCAACTTCC AGAAGACTAT TATAAAAATA AG - #GATAACAC         360                                                                           - AGGTAGAATT TATCAAGTAT ACATGTCTAA TCTTTTATCT GCACTATTGG GT - #GAGAATGG         420                                                                           - TGATCAAATT TCTAAAGATA TGGCAAATGA TTTTACCCAG AACGAACTGG AG - #TTTGAGGT         480                                                                           - CAACGTCTTA AAAATACCTG GGATATTCCT GATCTTGAGA ATAAACTATT GG - #AAGATTTA         540                                                                           - TTCAGATGAA GATAAATTAT TAGCACTATA TTTCTTTGCT TCACAAGAAC TT - #CCAATGGA         600                                                                           - GGCAAATCAA CAATCAAATG CAGCAAATTT TTTTAAAGTA ATTGATTTTT TA - #CTTATCTT         660                                                                           - ATCTGCTGTA ACATCACTGG GAAAAAGGAT TTTTTCAAAA AATTTTTACA AT - #GGTCTAGA         720                                                                           - AACTAAATCA TTAGAGAATT ATATTGAGAG AAAAAAACTT TCTAAACCTT TC - #TTTCGACC         780                                                                           - ACCGCAGAAG TTACCTGATG GCAGAACAGG CTACTTGGCC GGTCCAACAA AA - #GCGCCTAA         840                                                                           - ATTGCCAACA ACGTCTTCTA CAGCAACAAC GTCTACAGCA GCTTCATCTA AT - #TGGAGAGT         900                                                                           - TAGTTTGCAA AAACCTTAGA GATAACCCAT CCAGAAATAC ATTTATGAAA AT - #GGATGATG         960                                                                           - CTGCAAAACG AAAATATAGT TCATTTATAA AAGAGGTACA AAAGGGTAAT GA - #TCCACGTG        1020                                                                           - CAGCAGCAGC AAGTATTGGT ACAAAAAGCG GCAGTAACTT CGAAAAACTG CA - #AGGTAGAG        1080                                                                           - ATTTATATAG TATAAGACTA AGCCAAGAAC ACAGGGTAAC ATTCTCCATA AA - #TAATACTG        1140                                                                           - ACCAAATAAT GGAGATCCAA AGTGTTGGAA CTCATTACCA AAATATATAA CC - #TGATTTAT        1200                                                                           - AGTAGTGATA AGACGTAAGA TAAATATGGA AGGTTGTAAT TCTATTGCAC TT - #CCTCAGAG        1260                                                                           #     1272                                                                     - (2) INFORMATION FOR SEQ ID NO:7:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #acids    (A) LENGTH: 383 amino                                                          (B) TYPE: amino acid                                                           (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: protein                                              #ID NO:7: (xi) SEQUENCE DESCRIPTION: SEQ                                       -      Met Val Ile Lys Pro Val Thr Thr - # Pro Ser Val Ile Gln Leu Thr         Pro                                                                            #   15                                                                         -      Asp Asp Arg Val Thr Pro Asp Asp - # Lys Gly Glu Tyr Gln Pro Val         Glu                                                                            #                 30                                                           -      Lys Gln Ile Ala Gly Asp Ile Ile - # Arg Val Leu Glu Phe Lys Gln         Thr                                                                            #             45                                                               -      Asn Glu Ser His Thr Gly Leu Tyr - # Gly Ile Pro Tyr Arg Ala Lys         Lys                                                                            #         60                                                                   -      Val Ile Ile Ala Tyr Ala Leu Ala - # Val Ser Gly Ile His Asn Val         Ser                                                                            #     80                                                                       -      Gln Leu Pro Glu Asp Tyr Tyr Lys - # Asn Lys Asp Asn Thr Gly Arg         Ile                                                                            #   95                                                                         -      Tyr Gln Val Tyr Met Ser Asn Leu - # Leu Ser Ala Leu Leu Gly Glu         Asn                                                                            #                110                                                           -      Gly Asp Gln Ile Ser Lys Asp Met - # Ala Asn Asp Phe Thr Gln Asn         Glu                                                                            #            125                                                               -      Leu Glu Phe Glu Val Asn Val Leu - # Lys Ile Pro Gly Ile Phe Leu         Ile                                                                            #        140                                                                   -      Leu Arg Ile Asn Tyr Trp Lys Ile - # Tyr Ser Asp Glu Asp Lys Leu         Leu                                                                            #    160                                                                       -      Ala Leu Tyr Phe Phe Ala Ser Gln - # Glu Leu Pro Met Glu Ala Asn         Gln                                                                            #   175                                                                        -      Gln Ser Asn Ala Ala Asn Phe Phe - # Lys Val Ile Asp Phe Leu Leu         Ile                                                                            #                190                                                           -      Leu Ser Ala Val Thr Ser Leu Gly - # Lys Arg Ile Phe Ser Lys Asn         Phe                                                                            #            205                                                               -      Tyr Asn Gly Leu Glu Thr Lys Ser - # Leu Glu Asn Tyr Ile Glu Arg         Lys                                                                            #        220                                                                   -      Lys Leu Ser Lys Pro Phe Phe Arg - # Pro Pro Gln Lys Leu Pro Asp         Gly                                                                            #    240                                                                       -      Arg Thr Gly Tyr Leu Ala Gly Pro - # Thr Lys Ala Pro Lys Leu Pro         Thr                                                                            #   255                                                                        -      Thr Ser Ser Thr Ala Thr Thr Ser - # Thr Ala Ala Ser Ser Asn Trp         Arg                                                                            #                270                                                           -      Val Ser Leu Gln Lys Pro Arg Pro - # Ile Gln Lys Tyr Ile Tyr Glu         Asn                                                                            #            285                                                               -      Gly Cys Cys Lys Thr Lys Ile Phe - # Ile Tyr Lys Arg Gly Thr Lys         Gly                                                                            #        300                                                                   -      Ser Thr Cys Ser Ser Ser Lys Tyr - # Trp Tyr Lys Lys Arg Gln Leu         Arg                                                                            #    320                                                                       -      Lys Thr Ala Arg Arg Phe Ile Tyr - # Lys Thr Lys Pro Arg Thr Gln         Gly                                                                            #   335                                                                        -      Asn Ile Leu His Lys Tyr Pro Asn - # Asn Gly Asp Pro Lys Cys Trp         Asn                                                                            #                350                                                           -      Ser Leu Pro Lys Tyr Ile Thr Phe - # Ile Val Val Ile Arg Arg Lys         Ile                                                                            #            365                                                               -      Asn Met Glu Gly Cys Asn Ser Ile - # Ala Leu Pro Gln Arg Pro Leu         #        380                                                                   __________________________________________________________________________ 

We claim:
 1. An isolated polynucleotide that encodes an insecticidal toxin of Xenorhabdus nematophilus, said polynucleotide comprising the nucleotide sequence of SEQ ID NO: 1 from base 1 to base
 392. 2. The polynucleotide of claim 1, further comprising, at a position 3' of said nucleotide sequence, the second nucleotide sequence of SEQ ID NO: 1 from base 456 to base
 830. 3. A purified insecticidal toxin from Xenorhabdus nematophilus, wherein said toxin is effective against Galleria mellonella larvae and comprises the amino acid sequence of SEQ ID NO: 2 from residue 1 to residue
 131. 4. An isolated and purified expression vector comprising a promoter operatively linked to the nucleotide sequence of SEQ ID NO: 1 from base 1 to base
 392. 5. The expression vector of claim 4, further comprising, at a position 3' of said nucleotide sequence, the second nucleotide sequence of SEQ ID NO: 1 from base 456 to base
 830. 6. A bacterium or fungus transformed with the vector of claim
 4. 7. A bacterium or fungus transformed with the vector of claim
 5. 8. An infectious insect virus comprising the exogenous nucleotide sequence of SEQ ID NO:1 from base 1 to base 392, which nucleotide sequence is expressed upon infection of an insect cell.
 9. The insect virus of claim 8, further comprising, at a position 3' of said nucleotide sequence, the second nucleotide sequence of SEQ ID NO: 1 from base 456 to base
 830. 10. An isolated polynucleotide that encodes an insecticidal toxin from Xenorhabdus nematophilus, wherein said toxin kills Galleria mellonella larvae and comprises the amino acid sequence of SEQ ID NO: 2 from residue 1 to residue
 131. 